Anti-disturbance fuse



Dec. 10, 1968 o. E. HART ETAL 3,415,190

ANTI-DISTURBANCE FUSE Filed Dec. 9, 1964 2 Sheets-Sheet l l l/l/IVI/l/I FIG. 3A. f 36 14 k 28 INVE NTORS. OTHO E. HA RT LEWIS W. IMM BY V. C. MULL E R ATTOR NEY.

Dec. 10, 1968 o. E. HART ETAL 3,415,190

ANTI -DISTURBANCE FUSE Filed Dec. 9, 1964 2 Sheets-Sheet 2 FIG. 6.

will/1111117111114 TRAVEL FIG. 5.

FIG. 5A.

TRAVEL INVENTORS OTHO E HART LEWWS W.|MM

BY'N.C.MULLER ATTORNEX United States Patent 3,415,190 ANTI-DISTURBANCE FUSE Otho E. Hart, China Lake, and Lewis W. 1mm, North Hollywood, 'Calif., assignors to the United States of America as represented by the Secretary of the Navy Filed Dec. 9, 1964, Ser. No. 417,255 6 Claims. (Cl. 102-702) The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

This invention relates to anti-disturbance fuses for initiating explosives and more particularly to a fuse which incorporates an arming delay, will thereafter initiate the explosive if disturbed, and if not disturbed, will initiate an explosive after a predetermined delay.

In certain types of warfare it is tactically desirable to mine a land area to inflict damage upon enemy personnel entering the same, or to deter their entering the area when it is learned that it has been mined. It is also desirable to initiate the mines after a predetermined time, to thus clear it of explosives to permit re-entry into such area. Thus, an area may be rendered uninhabitable for a time unknown to the enemy, but for a time known to the personnel who plant the mines, thus conferring a tactical advantage upon the latter. To obtain maximum eifectiveness it will be apparent, however, that the time at which the mines will become self-destructive and the area again be rendered habitable should be known to a close degree of accuracy. Time delay, self-restruct fuses may be fabricated which are highly accurate, such as by employing clockwork escapements, but they are usually complicated, expensive, and fragile. These criteria defeat their practicability, particularly due to fragibility, where it is desired to mine an area by dropping from aircraft.

Objects of the invention are to provide a fuse of the type referred towhich is extremely simple in construction, inexpensive of manufacture, and extremely rugged to thus withstand shock forces, such as by dropping from aircraft.

Another object is to provide a fuse of such type which will cause self-destruction after a predetermined time and independent of climatic temperature changes during the time it is armed.

A further object is to provide a fuse of compact dimensions such that it may be incorporated in mines of all sizes including articles of small size which invite the enemy to pick up or otherwise disturb the same.

Still further objects, advantages, and salient features will become more apparent from the description to follow, the appended claims, and the accompanying drawing, in which:

FIG. 1 is an end elevation of a fuse embodying the subject of the invention,

FIG. 2 is an enlarged section taken on line 22, FIG. 1;

FIG. 3 is an enlarged section taken on line 3-3, FIG. 1,

FIG. 3A is a section like FIG. 3, showing another position of parts;

FIG. 4 is an enlarged section taken on line 44, FIG. 1;

FIG. 5 is an enlarged section taken on line 5-5, FIG. 4, at one temperature;

FIG. 5A is a like section at another temperature;

FIG. 5B is a like section at still another temperature; and

FIG. 6 is a schematic wiring diagram of the invention.

Referring now to the drawing, and first to FIGS. 1 and 6, the principal components of the invention comprise battery 10, capacitor 12, electrically activated detonator 3,415,193 Patented Dec. 10, 1968 14, arming switch 16, tremblor or anti-disturbance switch 18 and self-destruct switch 20, electrically connected as shown, all contained within a housing 22.

In the operation of the device, safety or arming pin 24 is manually removed from the housing which starts movement of the arming switch and self-destruct switch toward their closed positions, the arming switch having a short delay time, of say the order of minutes, and the selfdestruct switch having a delay time of say the order of a month or less. When the arming switch closes, the detonator may be activated by closing of the trembler switch by vibration or other inertia effects, such as by picking up the device from its position of repose. In event the detonator is not activated by such effects, the selfdestruct switch will eventually close and activate the etonator.

Referring now to FIGS. 1 and 2, housing 22, which may be of molded electrically insulating plastic material, is provided with a cavity 26 which receives the battery which may comprise a pair of series connected 1 volt miniature dry cells 10.

The arming switch 16, shown in unarmed position in FIG. 3 and in armed position in FIG. 3A, comprises a piston 28, rectangular in cross-section, in which is housed detonator or squib 14 comprising a powder charge and initiating electric bridge wire of conventional form. Arming is effected when contact 30 engages terminal 32. Cylinder 34 contains a fluid which leaks through the clearance space between the piston and cylinder, from one side of the piston to the other, as the piston is urged by a spring 36. As shown in FIG. 3A, the spring has moved the piston to its limit position, contacts 30, 32 which comprise switch 16 now being closed. If detonator 14 is now activated by closing of the trembler switch, diaphragm 38 is ruptured, detonating booster lead charge 40, which in turn detonates the main charge of explosive (not shown) which may be disposed adjacent the fuse device.

As best shown in FIG. 4, trembler switch 18 comprises a metal tube 42 containing a metallic weight 44 supported by a resilient wire 46, such as piano wire, insulatingly supported at one end within the tube. As will be apparent, any slight vibration of housing 22 in any direction transverse to the wire will cause weight 44 to contact the tube, thus closing switch 18 and initiating detonator 14.

As previously set forth, self-destruct switch 20 has a delay time greatly in excess of the delay time of the arming switch. Since considerable ambient temperature changes may be encountered during a delay of, say a month or less, it is essential that the self-destruct switch be constructed to compensate for such temperature changes and provide a substantially constant time delay irrespective of ambient temperature. Referring to FIGS. 4, 5, 5A and 5B the sel-f-destruct switch comprises a brass tube 48 which slideably receives a nylon piston 50 having conical end surfaces 52, 52 disposed adjacent mating surfaces of a brass screw 54 to which is affixed a nut 56 having apertures 58 therein. When the nut is properly positioned on the screw, it is rendered immovable by staking or other appropriate locking means.

Referring now to FIG. 5A and assuming a temperature of say F., end surface 52, 52 are in contact with the screw and nut and the sole passage between opposite ends of the piston is annular clearance space 60 (shown greatly exaggerated) which forms a metering passage to control the rate of flow of the fluid around the piston. Assuming now that the temperature increases, say to F, the piston increases in diameter at a greater rate than the increase in diameter of the tube thus reducing the annular metering passage. Also, since the piston is restrained against free longitudinal expansion by the conical surfaces on the screw and nut it bows slightly at its midpoint as shown in FIG. 5. Since the fluid now has a lower viscosity due to the increased temperature the rate of flow through the smaller passage will be substantially the same as in FIG. 5A. Assuming next, that the temperature drops to say 60, the piston shrinks relative to the tube, increasing the annular clearance space. Also, it shrinks in a longitudinal direction separating faces 52, 52 from the screw and nut surfaces, providing an additional passage 62 through the piston. Fluid now flows through passages 60, 62, and since the viscosity of the fluid has now increased with the decrease in temperature, the rate of flow is substantially the same as it was at the two higher temperatures previously described.

The fluid employed in the arming and self-destruct switches is highly refined dimethyl-polysiloxane, a silicone similar to bouncing putty, manufactured by the General 1 Electric Company, and having a viscosity of 5 to million centistokes, depending upon the time delay desired, particularly in the self-destruct switch, the accuracy of the time delay of which is considerably more important or critical than that of the arming switch.

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.

What is claimed is:

1. Timing apparatus comprising;

(a) a cylinder, having a closure at one end thereof,

(b) a circular piston slideably disposed within a cylinder, there being an annular passage between the piston and cylinder,

(c) said piston being of a material having a greater coefiicient of expansion than the cylinder,

(d) a liquid filling the space between the closure and piston having a viscosity which decreases with increase in temperature,

(e) a spring urging said piston in the direction of said closure, whereby said fluid is metered through said passage,

(f) said piston having a central aperture between its ends with frusto-conical surfaces at opposite ends of the aperture,

(g) a valving member disposed within said aperture having frusto-conical surfaces engageable with said surfaces at opposite ends, the frusto-concial surfaces on the piston and valving member at the end facing said closure forming a variable orifice valve, said valving member being of a material having the same coefficient of expansion as said cylinder,

(h) the construction and arrangement being such that when the apparatus cools to a predtermined temperature liquid flows through said annular passage and also through said central aperture and flows only through said annular passage at higher temperatures, said annular passage decreasing in size as the temperature increases,

(i) whereby, as the viscosity of said liquid changes with temperature, it is metered from said cylinder at a substantially constant rate, to thereby provide a substantially constant time for said piston to move a predetermined distance, and

(j) means actuated by the piston when it moves said predetermined distance.

2. Apparatus in accordance with claim 1 wherein said cylinder and valving members are constructed of brass, said piston is constructed of nylon, and said fluid is dimenthyl-polysiloxane.

3. Apparatus in accordance with claim 1 including an electrically initiated detonator, said means comprising an electric switch adapted to initiate said detonator when the piston moves to said predetermined position, said detonator adapted to initiate an explosive to thereby automatically destroy itself in a predetermined time after said piston begins to move.

4. Apparatus in accordance with claim 1 forming a part of an inti-disturbance fuse, said fuse including a sensitive inertia operated electric switch adapted to be closed when the apparatus is moved from a position of repose, said electric switch adapted to initiate an explosive when it closes.

5. Apparatus in accordance with claim 4 including a time delay arming switch adapted to move to closed position a predetermined time after commencement of its operation, said inertia operated switch being ineffective until after expiration of said predetermined time.

6. An anti-disturbance fuse for initiating an explosive charge, comprising;

(a) a casing containing an electric battery, an arming timer, a self-destruct timer, and a sensitive inertia actuated anti-disturbance switch,

(b) said arming timer and self destruct timer compris ing a pair of parallel cylinders, one being an arming cylinder and the other a self-destruct cylinder, each having a spring urged piston in same and a fluid adapted to be metered from one side of a piston to the other under urge of its spring to thereby permit the pistons to move predetermined distances within their cylinders, the piston in the arming cylinder adapted to close a switch after a relatively short time after commencement of its movement to arm the fuse, and the piston in the self-destruct cylinder adapted to close a relatively long time after commencement of its movement to initiate an explosive,

(c) a pull pin extending across both cylinders for blocking movement of the pistons and for permitting the pistons to move under urge of their springs when the pull pin is removed from the fuse,

(d) said anti-disturbance switch comprising a cylindrical elongated metallic tube, a metallic resilient wire disposed axially of the tube and insulatingly supported at one end of the same, the other end of the wire having a circular metallic weight thereon disposed centrally of the tube with an annular space between its periphery and the tube, the weight adapted to move relative to the tube in all directions in a plane perpendicular to the longitudinal axis of the tube when the fuse is disturbed, to thereby engage the tube and close an electric circuit to initiate an explosive,

(e) and an electric circuit including said battery and switches operated by said pistons for arming the fuse a short time after said pull pin is removed, for threafter initiating an explosive if the use is disturbed, and for initiating the explosive a relatively long time after said pull pin is removed in event the fuse has not been disturbed.

References Cited UNITED STATES PATENTS 2,764,648 9/1956 Gascoine et al. 200-34 X 2,821,268 1/1958 De Carbon 188--100 2,968,240 1/1961 Booth l02l6 2,994,271 8/1961 Silver et al. 10282 X 3,171,245 3/1965 Breed 10282 X FOREIGN PATENTS 1,115,057 4/ 1956 France.

BENJAMIN A. BORCHELT, Primary Examiner.

G. H. GLANZMAN, Assistant Examiner.

US. Cl. X.R. 

6. AN ANTI-DISTURBANCE FUSE FOR INITIATING AN EXPLOSIVE CHARGE, COMPRISING; (A) A CASING CONTAINING AN ELECTRIC BATTERY, AN ARMING TIMER, A SELF DESTRUCT TIMER, AND A SENSITIVE INERTIA ACTUATED ANTI-DISTURBANCE SWITCH, (B) SAID ARMING TIMER AND SELF DESTRUCT TIMER COMPRISING A PAIR OF PARALLEL CYLINDERS, ONE BEING AN ARMING CYLINDER AND THE OTHER A SELF-DESTRUCT CYLINDER, EACH HAVING A SPRING URGED PISTON IN SAME AND A FLUID ADAPTED TO BE METERED FROM ONE SIDE OF A PISTON TO THE OTHER UNDER URGE OF ITS SPRING TO THEREBY PERMIT THE PISTONS TO MOVE PREDETERMINED DISTANCES WITHIN THEIR CYLINDERS, THE PISTON IN THE ARMING CYLINDER ADAPTED TO CLOSE A SWITCH AFTER A RELATIVELY SHORT TIME AFTER COMMENCEMENT OF ITS MOVEMENT TO ARM THE FUSE, AND THE PISTON IN THE SELF-DESTRUCT CYLINDER ADAPTED TO CLOSE A RELATIVELY LONG TIME AFTER COMMENCEMENT OF ITS MOVEMENT TO INITIATE AN EXPLOSIVE, (C) A PULL PIN EXTENDING ACROSS BOTH CYLINDERS FOR BLOCKING MOVEMENT OF THE PISTONS AND FOR PERMITTING THE PISTONS TO MOVE UNDER URGE OF THEIR SPRINGS WHEN THE PULL PIN IS REMOVED FROM THE FUSE, 